Bizarre 'Mold Pigs' Trapped in 30-Million-Year-Old Amber Are An Entirely New Family of Animals

Researchers have identified microscopic ancient creatures—dubbed "mold pigs"—in 30-million-year-old amber which represent not only a new species, but an entirely new family of invertebrates—animals without backbones.

George Poinar Jr. from Oregon State University and Diane Nelson of East Tennessee State University discovered several hundred individuals in amber which was found in the Dominican Republic, according to a study published in the journal Invertebrate Biology.

The pair described the animals as "mold pigs" due to the fact that they bear a resemblance to true pigs and consumed mold.

In scientific terms, they have been described as Sialomorpha dominicana. The first part of this name derives from the Greek words for fat hog ("sialos") and shape ("morphe") while the second part refers to the country in which the amber was found.

"Every now and then we'll find small, fragile, previously unknown fossil invertebrates in specialized habitats," Poinar said in a statement. "And occasionally, as in the present case, a fragment of the original habitat from millions of years ago is preserved too."

The mold pigs would have lived in warm, moist habitats alongside pseudoscorpions, fungi, roundworms and protozoa—single-celled organisms.

The creatures—which are invisible to the naked eye—look like similar to modern tardigrades, which are known for their extreme survival abilities. However, the two animals are not closely related.

"The mold pigs can't be placed in any group of currently existing invertebrates—they share characteristics with both tardigrades, sometimes referred to as water bears or moss pigs, and mites but clearly belong to neither group," he said.

The mold pigs measured around 100 micrometers long—about as thick as a human hair. They had flexible heads and four pairs of legs. Most of the time, they ate mold—a type of fungus—although they may have also preyed on other tiny invertebrates. To grow, they shed their exoskeleton, according to the researchers.

"No claws are present at the end of their legs as they are with tardigrades and mites," Poinar said. "Based on what we know about extant and extinct microinvertebrates, S. dominicana appears to represent a new phylum.

"They appear to be hermaphroditic since no males were found among the several hundred specimens in the amber," he told Newsweek. "The eggs hatch inside the females rather than in the environment."

Despite the fact that the researchers were able to learn a lot about the mold pigs due to the high number of fossils they found, there is still a lot to learn about the animals, they say.

"The structure and developmental patterns of these fossils illustrate a time period when certain traits appeared among these types of animals. But we don't know when the Sialomorpha lineage originated, how long it lasted, or whether there are descendants living today," Poinar said.

Mold pig, Sialomorpha dominicana
Fossils preserved in Dominican amber reveal a new family, genus and species of microinvertebrate, a discovery that shows unique lineages of the tiny creatures were living 30 million years ago. George Poinar Jr.